Environmental Science: Nano最新文献

Herein we developed nanofiber composite membranes made of polyacrylonitrile (PAN) and iron oxide nanoparticles using a one-pot electrospinning synthesis method for application in point-of-use (POU) water treatment devices targeting both dissolved and particulate lead. With the goal of optimizing lead removal while minimizing raw material costs, we explored different commercially available iron oxides and incorporated simple organic acids (OAs) [e.g., ortho- and tera-phthalic acid (PTA and TPTA) and ethylenediaminetetraacetic acid (EDTA)] based on our previous observation that sodium dodecyl sulfate (SDS) promotes enrichment of iron oxide at the electrospun nanofiber surface (i.e., surface segregation). From sorption isotherm studies, we found that increasing iron oxide loading led to higher lead uptake (e.g., PAN with 5 wt% iron oxide exhibited a lead removal capacity of 10 mg g⁻¹ of mat versus 5 mg g⁻¹ for 1 wt% iron oxide). PAN with 5 wt% iron oxide (3.3 mg lead removal per $) also resulted in better cost-normalized lead removal than PAN with 1 wt% iron oxide (1.0 mg lead removal per $). The integration of OAs further improved performance; for example, PAN with 5 wt% iron oxide and 3 wt% PTA achieved approximately 40 mg g⁻¹. From nanofiber characterization via microscopic (SEM and TEM) and spectroscopic (XPS and FTIR) tools, OAs increase lead uptake through a combination of pathways: (1) stabilizing iron oxide particles and improving their dispersion in electrospinning sol gels; (2) promoting surface segregation that increases iron oxide concentration at the nanofiber surface; (3) functioning as a porogen that increases composite surface area; and (4) introducing some additional lead binding sites (e.g., carboxylates) within the nanofiber. Simulating point-of-use application in a dead-end filtration system (effective filter area of 12.6 cm², filter thickness of 120 μm, and flow rate of 20 mL min⁻¹), we observed lead-free permeate with just 0.24 g of our optimal formulation when challenged with 4 L of 150 μg L⁻¹ soluble lead solution and 90% removal when this filter was challenged with a feed solution containing both dissolved and particulate lead (160 μg L⁻¹ total lead with 30% of particulate lead; >0.1 μm). Our study highlights the potential for OAs to enhance the performance of polymer–metal oxide nanofiber composites via a one-pot synthesis that will help to minimize production costs for high-performing materials.

Recent studies have highlighted the ecotoxicological effects of conventional primary nanoplastics (NPLs); however, the impacts of secondary NPLs and oligomers (Olig), especially those derived from biodegradable plastics, formed through fragmentation and natural degradation processes (e.g., photooxidation) remain underexplored. This gap is partly due to challenges in producing sufficient quantities for toxicity testing. An improved method to generate non-photooxidized (NP) and photooxidized (P) secondary NPLs and Olig from polybutylene adipate co-terephthalate (PBAT), a biodegradable plastic commonly used in agriculture mulching, which involves the mechanical breakdown of PBAT-microbeads with or without prior photooxidation is presented. PBAT was irradiated at ∼9.34 kW m⁻² (approximately 120 times the solar irradiance) for 96 h, irradiation that corresponds to ∼16 months of average sunlight in the Iberian Peninsula (7.7 kWh m⁻² per day). The toxicological effects on Chlamydomonas reinhardtii, a model green microalga of primary producers in freshwater ecosystems, were also assessed. The protocol yielded 0.199 mg of secondary NP-PBAT-NPLs and 10.275 mg of NP-PBAT-Olig per gram of PBAT-microbeads. PBAT-NPLs presented irregular spherical morphologies and hydrodynamic sizes ranging from 56.71 to 69.86 nm. HPLC and MALDI-TOF analysis identified linear and cyclic Olig, ranging from dimers to 19 repeated-units Olig. PBAT-NPLs and PBAT-Olig exhibited negative surface charges, suggesting colloidal stability in water. While PBAT-NPLs and PBAT-Olig did not inhibit algal growth in the short term, they induced reactive oxygen species overproduction at the environmentally relevant concentration of 0.01 mg L⁻¹ and caused membrane depolarization, impaired photosynthesis and lipid peroxidation at 10 mg L⁻¹. Non-photooxidized PBAT-NPLs exhibited the highest toxicity, followed by photooxidized PBAT-NPLs and both non-photooxidized and photooxidized PBAT-Olig. This study provides an efficient method for producing reference secondary NPLs and Olig and underscores the potential risks of PBAT towards primary producers in freshwater ecosystems.

Emissions from industrial activities have led to the significant accumulation of volatile organic compounds (VOCs) in the atmosphere, raising substantial concerns due to their serious threats to human health and the global environment in recent years. Among the various strategies for VOC abatement, adsorption technology has emerged as a promising approach for effectively removing VOCs from contaminated air. However, the adsorption behavior and mechanisms for different VOC species remain poorly understood. Herein, the adsorption characteristics of eight typical VOC categories (C ≤ 8 atoms) commonly emitted by the petrochemical industry were systematically investigated using density functional theory (DFT) calculations at the electronic and atomic levels on monolayer MoS₂. The VOC categories analyzed include alkanes, alkenes, alkynes, alcohols, aldehydes, carboxylic acids, ketones and aromatic hydrocarbons. Our research was aimed at investigating the adsorption behaviors of various types of VOCs, including those with varying carbon chain lengths within the same category. Results demonstrated that the unique structural properties of the MoS₂ monolayer not only provided excellent adsorption capabilities but also exhibited distinct responses to the eight aforementioned VOC categories. The adsorption energies of the VOCs followed a distinct hierarchical order, alkanes < aromatic hydrocarbons < alkynes < aldehydes < ketones < alkenes < alcohols < carboxylic acids, with the values ranging from −0.25 to −1.19 eV. In different VOC adsorption systems, the distance between the rightmost peak of the density of states (DOS) and the Fermi level ranged from −1.42 to −0.17 eV. Additionally, for a given VOC category, it was observed that an increase in carbon chain length correlated with an increase in adsorption energy. A predictive fitting curve for the adsorption energy of VOCs was derived and expressed as E_ads (E_v) = −0.13X − 0.12, where X represents the number of carbon atoms. Through comprehensive analyses involving charge density differences, DOS and Mulliken charge analysis, the underlying mechanisms correlating adsorption energy with both VOC species and carbon chain length were elucidated. Our research highlights the potential of MoS₂ as a promising candidate for selective VOC adsorption and provides a theoretical framework for the development of high-performance VOC adsorbents.

Metastable β-Bi₂O₃ exhibits high catalytic performance due to its suitable band gap, greater dielectric permittivity and conductivity. However, the difficultly in preparing β-Bi₂O₃ and β-Bi₂O₃ based materials is still a problem to be overcome. In this work, porous Bi/β-Bi₂O₃@carbon photocatalysts were prepared for the first time by using an atmosphere switching strategy during the post-cooling of metal–organic framework (MOF) pyrolysis. The crystal phase structure and composition of Bi/β-Bi₂O₃@carbon could be easily adjusted by simply switching the cooling atmosphere from N₂ to air when cooled to different temperatures. The photocatalytic activities of the material were evaluated by degradation of emerging pollutant fluorescent whitening agent (FWA) 351 under simulated solar light irradiation. It was observed that 10 mg L⁻¹ FWA 351 was completely degraded within 4 h using the optimal photocatalyst. The mineralization efficiency reached 60% in 6 h. Active species trapping experiments confirmed that hole oxidation was responsible for the degradation of FWA 351. The increased activity was due to the improved visible light utilization resulted from the reduced bandgap of Bi/β-Bi₂O₃@carbon and the surface plasmon resonance effect of bismuth metal, as well as the facilitated interfacial electron migration and charge carrier separation through multi-interface transfer paths. The proposed strategy provides new ideas for designing and synthesizing functional materials. The efficient degradation and mineralization of FWA 351 with Bi/β-Bi₂O₃@carbon also confirmed its potential for future application in wastewater treatment.

Microplastic (MP) pollution has become a serious environmental problem in the current decade. Unfortunately, wastewater treatment plants are not favorable for treating MPs. Therefore, it is necessary to develop methodologies to treat MPs in water efficiently. Photocatalytic (PC) and photo-Fenton (PF) processes are among the promising treatment methodologies that utilize reactive oxygen species (ROS) to degrade MPs. In this study, TiO₂ aerogel powders (TiAP) were prepared by lyophilization and subsequent annealing of peroxo-titanic acid gels, followed by modification with Fe at the surface for the PC/PF-based degradation of MPs. Fe-modification on TiAP boosts the PC activity and activates the PF-based process in the presence of H₂O₂. The degradation of polystyrene (PS) MPs was evaluated using attenuated total reflection infrared (ATR-IR) spectroscopy, total organic carbon (TOC) analysis, thermogravimetric analysis coupled with differential scanning calorimetry and mass spectrometry (TGA-DSC/MS), nuclear magnetic resonance (NMR) spectroscopy, and high-performance liquid chromatography with high-resolution mass spectrometry (HPLC-HRMS). Photo-induced degradation of the PS MPs was evaluated by monitoring the changes in the carbonyl/peroxyl index (CI/PI) recorded by ATR-IR spectroscopy and the mass loss measured by TGA-DSC/MS techniques. Interestingly, the samples with higher CI value changes affected the total mass residue, while samples with lower changes in the CI value did not alter the total mass residue after the photo-induced treatment. Further, NMR spectra confirmed the formation of new peaks due to the oxidative degradation of PS MPs, especially between 0.8 and 1.3 ppm. Additionally, by-products formed after the photo-induced treatment process analyzed by the HPLC-HRMS technique indicate the degradation of PS MPs. The indirect techniques of electron paramagnetic resonance (EPR) spectroscopy revealed the ROS contributing to the oxidation of PS MPs during the PC and PF treatment process using Fe-modified TiAP. This study's findings have the potential to significantly influence future research and environmental policies by providing better insights into preparing efficient nanostructures for photo-induced degradation of MPs.

Graphene oxide (GO) nanosheets have emerged as a potent nanomaterial for a range of applications, such as antibacterial and antibiofilm applications. Besides, microplastics are emerging as a chronic pollutant originating from the aggrandized usage of plastics, posing serious risks to living beings and the environment. In view of this issue, the individual toxicological impacts of GO nanosheets and polystyrene (PS) have received substantial research attention, yet the mechanistic details and toxicological effects of GO and PS combined in a hybrid system remain unknown. Hence, this study evaluated the in vivo biotoxicity of a lab mimic green-synthesized GO@PS hybrid using embryonic zebrafish through experimental and computational approaches. The physiochemical characterization of the GO@PS verified the synthesis of a stable 1433.0 ± 268.0 nm-sized GO@PS hybrid with a zeta potential of −47.3 ± 5.7 mV. Mechanistic analysis results deduced that the toxicological impact caused an induced apoptosis due to dysregulated oxidative stress led by the hypoxic condition created due to blockage of chorion by attachment and accumulation of GO@PS. The study elucidated the in vivo toxicity of GO, PS and GO@PS at cellular and molecular levels to devise measures for the safe usage of GO and PS in terms of environmental and human health aspects.

The development of safe nanomaterials has become a significant concern in various industry sectors using advanced materials. While there is variability in the definitions of Safe(r) by Design (SbD), the general concept is to minimise environmental, health and safety concerns by implementing appropriate measures at an early stage of product design to control exposure and hazard, thus reducing risks. The SbD product strategy applied in this paper refers to the mitigation of exposure by the identification of release scenarios during the use and the end of life of nano-enabled products (NEPs) that include engineered nanomaterials (ENMs). This strategy was applied to the development of a photocatalytic mineral paint containing a TiO₂ engineered nanomaterial. This ENM was then incorporated into a mineral matrix-based paint for photocatalytic application. The different paint formulations were applied to standardised substrates and artificially weathered in an accelerated weathering chamber with controlled parameters. Mechanical solicitation that simulates the end of life (EoL) of the paint, through abrasion tests, was performed to assess the potential emission of airborne particles that could lead to human or environmental exposure. The release evaluation confirms that paints with TiO₂ nanoparticles without SbD coating release more nanometric particles due to strong matrix degradation. TiO₂ nanoparticles coated with PEG or grafted onto CNCs do not completely prevent the degradation of the paint surface during ageing. However, this degradation does not necessarily lead to an increase in aerosol emission. The coating degradation during accelerated ageing limits the degradation of the paint matrix, preventing the release of unbound TiO₂ nanoparticles. Understanding the mechanisms of release and how they are influenced by ENMs, the matrix material and the process characteristics are crucial for the exposure and risk assessment approach in occupational settings involving engineered nanomaterials. Moreover, establishing release rates makes it possible to increase the reliability of SbD e-infrastructure for performance testing and the implementation of Safe-by-Design approaches in the nanotechnology supply chain.

Positively charged nanoplastics are more toxic to microorganisms than their negatively charged counterparts, prompting further investigation into their antimicrobial properties. While many studies have shown that positively charged nanoplastics bind to bacteria, the fate of these nanoplastic coatings during bacterial growth remains unclear. Here, we report how amine-modified polystyrene nanoplastics (PS-NH₂) reduce the viability of the plant growth-promoting rhizobacterium Bacillus subtilis and impair its ability to colonize plant roots. We found that upon exposure to PS-NH₂, the nanoplastics form stable, multilayer coatings on the surface of the bacteria. In response, B. subtilis initiates processes to remove these nanoplastics—a behavior heavily influenced by their growth environment, whether at air or liquid interfaces. Consequently, we observed differential toxicity under varying growth conditions. Using tomato plant as a model system, we found that these nanoplastics severely inhibit bacterial attachment to plant roots. Our results demonstrate that nanoplastics can disrupt beneficial interactions between soil bacteria and plants, potentially compromising the effectiveness of microbial biofertilizers. Given that current practices introduce large amounts of plastics into agricultural areas, the adverse effects of nanoplastic pollution need to be mitigated.

The potential of piezoelectric polymer materials to harness minute-scale kinetic energy has garnered significant scientific interest. Their superior flexibility, ease of processing, and ability to conform to large areas and curved surfaces set them apart from inorganic materials. In this study, we developed a flexible, light-sensitive piezoelectric nano generator (PENG) using electrospun hybrid nanofibers composed of polyacrylonitrile (PAN) and α-Fe₂O₃. Through piezo response force microscopy (PFM), we characterized the piezoelectric properties of these nanofibers, noting a significant enhancement in the piezoelectric coefficient (d₃₃). We further investigated the application of three distinct nanostructured materials across three catalytic scenarios: piezoelectric, pyro catalytic, and photocatalytic. Our primary focus was on renewable energy generation and environmental remediation, particularly targeting the removal of organic pollutants. Our methods achieved an impressive removal efficiency of up to 95% for methylene blue (MB) dye. Additionally, we demonstrated the efficacy of integrating magnetic nanoparticles into electrospun nanofibers to improve the adsorption of heavy metals, specifically lead and copper contaminants. This research provides a comprehensive examination of nanomaterial-based energy harvesting systems, utilizing ferroelectric, sonocatalytic, and photocatalytic approaches.

Fragmented micro- and nanoplastics are widespread pollutants with adverse effects on the environment. However, the breakdown process does not end with micro- and nanoplastics but is expected to continue until carbon dioxide has been formed. During this process the plastics will undergo chemical changes and small molecules may be released. We have broken down small amine-modified (∅53 nm) and carboxyl-modified (∅62 nm) polystyrene nanoparticles by UV-B irradiation during 100 days. We see a decreasing size and an oxidation of the nanoparticles over time. Simultaneously, the acute toxicity to zooplankton Daphnia magna decreases. UV-B irradiation releases small, dissolved molecules that are toxic to Daphnia magna. The dissolved molecules include aminated alkyls, styrene remnants and secondary circularization products. The study shows that UV-B radiation can change the original toxicity of nanoplastics and release new toxic substances.